Identification of Key Intermediates during the NO and H2S Crosstalk Signaling Pathways

Specific Reactions of RSNO, HSNO, and HNO and Their Applications in the Design of Fluorescent Probes

Nitric oxide (NO)-derived species play essential roles in regulating cellular responses. Among these species, S-nitrosothiols (including RSNO and HSNO) and nitroxyl (HNO) are especially interesting. Owing to their high reactivity and short survival time, the detection of these molecules in biological settings can be challenging. In this regard, much effort has been invested in exploring novel reactions of RSNO/HSNO/HNO and applying these reactions to develop fluorescence probes. Herein, reported specific reactions of RSNO/HSNO/HNO are summarized and strategies used in the design of fluorescent probes are illustrated. The properties and potential problems of representative probes are also discussed.

Characterization of the simplest sulfenyl thiocyanate: isomers, spectroscopy and implications of astrophysical and biological relevance

Sulfenyl thiocyanate compounds, RSSCN, are involved in the human immune system biochemical processes. They are also the routes for the synthesis of complex S-containing species such as polypeptides, or symmetrical (RSSR) and unsymmetrical disulfides (RSSR'). At present, we have characterized the stable forms of the simplest sulfenyl thiocyanate compound, HSSCN, at the coupled cluster level. We found twenty-three isomers, for which we determined a set of structural parameters, anharmonic frequencies and reaction energies for the formation of the corresponding diatomic + triatomic and atomic + tetratomic fragments. We also discussed the implications of the present findings for biological entities containing a disulfide bridge, where we identified three isomers that may serve as prototypes. Similarities and differences with other S/N hybrid bioactive molecules are also discussed. From an astrophysical point of view, we expect HSSCN isomers to be present in astrophysical media, since several of their molecular fragments have already been detected. In sum, the present set of data can be used for the identification of HSSCN compounds and understanding the physical chemistry of sulfur containing molecules in vivo, in the laboratory and in astrophysical media.

Rational Design of a Dual-Reactivity-Based Fluorescent Probe for Visualizing Intracellular HSNO

Thionitrous acid (HSNO), the smallest S-nitrosothiol, is emerging as a potential key intermediate in cellular redox regulation linking two signaling molecules H₂ S and NO. However, the chemical biology of HSNO remains poorly understood. A major hurdle is the lack of methods for selective detection of HSNO in biological systems. Herein, we report the rational design, synthesis, and evaluation of the first fluorescent probe TAP-1 for HSNO detection. TAP-1 showed high selectivity and sensitivity to HSNO in aqueous media and cells, providing a useful tool for understanding the functions of HSNO in biology.